Our gym had a "Monkey Business" themed meet a couple years ago. There is a Monkey Business brand store kinda close by and they donated bags with their logos on it and such. There were bananas in the goody bags and blow up palm trees around the competition floor. It was fun because it was a unique theme... not the usual Halloween, Winter, Jingle Bells kinda thing.
A neighboring gym had a "Let the games begin" theme. The table clothes on the judges tables were twister boards, the names of each gymnast were on the wall cut out like scrabble letters and there were pads of paper with tic tac toe or dots games printed on them in the goody bags.